See this summary at their page in German (original) or English (machine-translated), via the DPR discussion thread here.
It is told that the excellent FA 43/1.9 Limited was used to do the test, but very unfortunately, the K-5 scores only 77.5% out of 100 for its IQ, which is the lowest amongst the Top 10 cameras.
So, I think there must be some good reasons behind, otherwise they won't put such a low score.
If you want to find out more, here is yet another first discussion at a large German forum, in German (original) or in English (machine-translated).
It seems that Pentax really has a hard-time to make a better upper model of DSLR even they are given a more advanced sensor! :-( Just very recently, we have just seen the IQ of the K-5 loses all in the shootout against the K-x with both the IR and DPR test images. Now, yet another famous magazine found and tells the same!
Oh, well, Pentax/Hoya, it's time for you to make a PRIME III, the PRIME II is just too old and dated! :-o Btw, still too mean to invest more? >:-x
Related:-
IQ and AF-C of the K-5 - I am Not Impressed! :-(